Fishbone Diagram

The fishbone diagram has a few other common names such as the cause and effect diagram, 5-Whys, and the why-why diagram.  These names are appropriate because this tool seeks to find the reasons why a particular event (the effect) was caused.

Analysis of underlying, or root cause, can be described as the method used to discover the essential deciding factor for an occurrence or flaw. This procedure is an area of interest because pinpointing the cause of an incident raises the probability of being able to produce or avoid it later on.

Many tools have been created to perform root cause analysis. A few of these tools include the Pareto chart, the fishbone chart, and failure mode and effects analysis (FMEA). Although all of these are valid and useful tools, we will take a closer look at the fishbone diagram.

By working from the end after figuring out the effect is the universal algorithm for coming up with a hypothesis. Usually, this is the incident or problem someone is trying to identify. Determining cause and effect is after that. If you ask yourself “What is causing this?”, you can come up with many different responses and you should catalog these. Upon the determination of the answer, you ask yourself again, “What causes this?”.  As such, you proceed until the root of the incident has been found.

Additional Resources

Creating the Fishbone Diagram

For every cause, the “why” question is asked till no more answers could be generated or until five generations have been completed (hence the 5 -Whys).  Due to it,the general shape of this diagram looks similar to a horizontal tree, or a fishbone. At the far right the original event (the effect) is listed. Then a horizontal line is drawn towards the left. From the horizontal line, the answers to the “why” questions are listed. Then the reasons for those answers are branched off. In most of the cases,the branches are a little bit slanted creating a look of a fishbone.

A company needs to reduce costs for the quarter. They do not order tools. The workers then do not have the tools they need to make the product efficiently. Without the proper tools, the workers take longer to complete their work and feel abused. This results in increased need for conflict management and incidentally higher wages so the price of the product must be raised. At a higher price, the customer refuses to buy the product. This is an example of the 5-why chain for a company that cost that company a customer.

After the root cause is uncovered, measures may be taken either to either guarantee that the root cause can be prevented in the future if the end result was a negative one, or else that it occurs again if there was a positive result. Only the symptoms of the problem get treated, as opposed to the cause, if the core of the problem is not correctly identified. Practices such as these could bring on extra costs, slower delivery, lesser quality, or all three.

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